Hi there,
I'm a UK Software developer specialising - and having vast commercial experience - in, Windows.
I specialise in C++ which is a high-performance low-level language that most of Windows it self is built on.
Your best bet is to understand Networking first; in particular Windows networking.
By customising your TCP/IP(or sFTP ) settings at an O/S level, you can actually speed up download speeds/times many times over(up to 2x - 10x times speed increase!).
Secondly, by using the correct download protocols and buffer sizes, you should be able to download this file in a few milli seconds; subject to network usage, bandwidth limitations and global internet traffic that flows thru your local area, obviously.
If you want me to help you, get back to me. :)
Cheers